[Morphology of IgA nephritis (Berger disease). Immunohistologic, light- and electron microscopic findings].

An IgA nephritis was diagnosed in 109 (24%) out of 445 renal biopsies with glomerular disease in the years from 1977 to 1985. The mean age of the patients in question was 29 years. The male:female sex ratio was 2.6:1. Immunohistologically, the characteristic branching mesangial IgA deposits were uniformly present. In addition 96% showed mesangial C3 and 54% mesangial IgG and/or IgM deposits. Besides, immunoglobulin and/or C3 deposits could be detected at glomerular basement membranes (20%). The histological types of IgA nephritis were minor glomerular abnormalities (10%), focal/segmental glomerulonephritis (29%), diffuse mesangioproliferative (58%), membranoproliferative (1 case), and sclerosing glomerulonephritis (2 cases). Additional tubulointerstitial lesions were found in 55%. Electron microscopically, in 53 cases under study, mesangial electron dense immunodeposits were seen. At the glomerular basement membranes, deposits could be found only in 23 examined cases (43%). The comparison of clinical data with morphological findings showed relationships between the degree of proteinuria and creatinine level increase with the histological type of IgA nephritis and with the degree of glomerular sclerosis, tubulointerstitial lesions, and electron microscopically proved glomerular basement membrane deposits. Hematuria seemed not to correlate with the morphological picture.